This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have developed a new method for solving photon transport problems that combines accuracy and increased speed when compared with conventional Monte Carlo simulations. This ?condensed history? method adapts a strategy routinely used to solve charged transport problems for radiation dosimetry, problems that would be prohibitively costly to solve conventionally. This method promises to be especially useful for tissue problems calling for computational models intermediate between classical diffusion theory and rigorous radiative transport. Gains in computational efficiency by factors of 4-5 over conventional simulation can be expected in many instances.